It is well known in the art of RF antennas, as commonly used onboard spacecraft, or in ground stations, for communication to transmit and/or receive electromagnetic RF signals, to use rotational joints to allow the RF signals to follow the rotation of a portion of the antenna feed chain. When some sections (or portions) or an antenna assembly needs to rotate relative to a fixed structure, the RF signals travelling or conveyed within the antenna feed system usually goes through rotating joints which induce RF signal losses as well as other drawbacks including electrical constraints (such as reduced signal frequency bands, Passive Inter-Modulation (PIM) products, limitations on RF power handling, etc.), and mechanical constraints (such as increase complexity, mass (which is especially of concern in space applications), etc.). This becomes even more troublesome when multiple axes of rotations are considered.
The above constraints get more important when a plurality of signals run through the rotating assembly, such as transmit (Tx) and receive (Rx) signals, and using both orthogonal polarizations of each one.
U.S. Pat. No. 4,511,868 of Munson et al. discloses a mechanically rotatable joint in which the wide ends of two similar horn structures are juxtaposed and joined by a rotary bearing extending there between which permits relative rotational motion between the two horn structures. A field shaping dielectric lens may be disposed at the relatively rotatable horn juncture to help ensure substantially planar wavefront shapes across the relatively rotatable joint. This rotatable joint does not allow rotations about different intersecting axes.
Accordingly, there is a need for an improved RF rotational joint using a matched horn coupler assembly.